8 x 100 = 800
8 times 100 is 800. Eight hundreds. If you prefer doubling, 100 doubles to 200, then 400, then 800, three steps in all. Working, calculator and neighbours below.
8 × 100 = 800
Adding 8 to itself 100 times gives the same answer.
The working
The 8 takes the two zeros from the 100 and becomes 800. As repeated addition it is eight hundreds: 100 + 100 + 100 + 100 + 100 + 100 + 100 + 100 = 800. Backwards, 800 divided by 8 = 100 and 800 divided by 100 = 8.
Doubling instead of multiplying
8 is 2 x 2 x 2, so three doublings do the job: 100 to 200, 200 to 400, 400 to 800. That puts this answer in the middle of a chain where every rung is double the one before it, from 4 x 100 = 400 up to 16 x 100 = 1600. If you can double, you never have to remember any of them.
800 as hours
Eight is the length of a standard working day, so 100 of those days is 800 hours. That is the useful reading of this product for anyone estimating a job in day rates. As continuous time it is smaller than it sounds: 800 hours is 33 days and 8 hours, because 33 x 24 = 792 and 792 + 8 = 800.
Either side of it
Just below sits 7 x 100 = 700, and just above 9 x 100 = 900. Every pair on the site is listed on the multiplication answers hub.